Piston engine



S. MEURER PISTON ENGINE April 10, 1956 2 Sheets-Sheet 1 Filed Aug. 18, 1954 INVENTOR Siegfried [Wearer ATTORNEYZS S. MEURER PISTON ENGINE April 10, 1956 2 Sheets-Sheet 2 Filed Aug. 18, 1954 INVENTOR Siegfried Meu/ er' @4117 m i ATTORNEYS United States Patent PISTON ENGINE Siegfried Meurer, Number-g, Germany, assignor to the firm Maschinenfabrlk Augshnrg-Nurnberg A. G., Numberg, Bavaria, Germany Application August 18, 1954, Serial No. 450,677

Claims priority, application Germany August 20, 1953 8 Claims. (Cl. 309-55) liable continuous and permanent lubrication of the working surface of the piston.

A special object of the invention is to provide means ensuring a uniform or at least satisfactory lubrication under varying working conditions of the engine as to its speed and temperature while avoiding an excessive oil consumption. A further object of the invention is to provide an effective cooling of the piston.

With these and other objects in view, this invention consists in the details of construction, combination of elements and operation hereinafter set forth and then specifically designated by the claims.

In order that those skilled in the art to which this invention appertains may understand how to make and use the same, I will describe its construction in detail, referring by numerals to the accompanying drawings forming part of this application, in which:

Fig. 1 is a perspective view of an arrangement having the invention applied thereto, with the piston partly in section,

Fig. 2 is a bottom view thereof, on a smaller scale,

Fig. 3 is a perspective view of the piston of Fig. 1,

Fig. 4 is a sectional view showing a modified form,

Fig. 5 is an elevation of a trunk piston having the in vention applied thereto, with trapezoidal bearing strips on the piston skirt, viewed toward the pressure side of the piston, i. e. the side which during the expansion stroke engages the wall of the cylinder, as indicated by the arrow A in Fig. 6,

Fig. 6 is a plan or end view thereof, viewed from the bottom,

Fig. 7 is an elevation similar to Fig. 5, but viewing onto the opposite pressure side of the piston, i. e., the side which engages the wall of the cylinder during'the compression stroke as indicated by the arrow B in Fig. 6.

Similar reference numerals denote similar parts in the different views.

Before referring to the figures in greater detail, the invention will be hereinafter explained in a general way, so as to facilitate the understanding thereof.

According to the present invention, provision 'is made to permit a circulation of the oil, but in such a manner that the oil is not returned in the conventional way from the cylinder wall towards the interior of the piston, through the openings provided in the oil scraper rings, but in an opposite direction. My forced circulation system lubrication is characterized by the combination of the following features:

1. The lubricating oil is injected or flung into the hollow space within the piston in the form of one or more jets.

2. The jet or jets are directed in such a way that at ice least a partof the lubricating'oil issues through the conventional passages provided in the annular oil groove of the oil scraper ring, towards the piston skirt or the cylinder wall, respectively.

3. The piston skirt is formed with relatively wide and shallow grooves or'channels or recesses having a depth of at least 0.5 mms. and extending at least from the region below the passages up to the free or lower end of the piston skirt, so as to ensure that the oil issuing from the passages and applied on the wall of the cylinder or passing directly into the channels is permitted to flow off freely in a downward'direction. Further important features relate to the shape and arrangement of the bearing surfaces of the piston, as will be hereinafter described with reference to the drawings.

Referring now to the drawings in greater detail, and first to Fig. 1, it'will be seen that the piston 1 has a cavity 2 forming a combustion chamber for cooperation with an injection nozzle'3. Said part of the arrangement is constructed in conventional manner and, therefore, need not be discussed in greater detail. The piston 1 is fitted with piston rings 4, 5, and 6 and with an oil scraper ring 7 which is formed with an annular oil groove 7a. Bores 8 in the piston and slits 9 in the oil scraper ring '7 cornmunicate with the groove 7a therein from the interior of the piston.

Through one or more nozzles 20, one or more oil jets 10- are injected into the hollow space within the piston, up to the internal top Wall la of the piston. By way of alternative, and as shown in Fig. 4, the oil may be in.- jected through nozzles 11b provided on the connecting rod 11 and fed with oil through one or more bores 11a.

The oil thus injected is distributed on the inner wall 1a of the piston 1, cooling the latter, and through the bores 8 and slots 9'the oil comes to the annular oil groove 7a and to the cylinder wall indicated at 12. For removing the oil, a pair of shallow groove-shaped recesses or channels 13 are symmetrically provided on the piston skirt, said grooves having a depth of at least 0.5 nuns. and extending in an axial direction at least from the annular oil groove 7a down to the lower end 14 of the piston; each of the channels 13 having a circumferential extension referring to the horizontal plane passing through the axis 15 of the piston or wrist pin iii-preferably of in such a Way that the angle of 90 is bisected by the axis of the piston or wrist pin, as best seen in Figs. 2 and 3. The depth of the channels 13 mustbe greater than 0.5 mms; in order that an oil layer can he formed on the bottom of the channels in the piston which layer is not impaired in regard to its effect as aforesaid by the oil layer deposited on the cylinder wall.

Inorder toinclude the piston rings into the return circuit, the recesses 13 may extend up to the second piston ring 5.

The operation of my forced' circulation system lubrication is as follows: The oil jets 10 injected into the interior of the piston impinge upon the inner surface'of the wall of the trunk piston and are distributed there, whereby a part of the oil passes through the bores 8 in thepiston and slots 9 in the annular oil groove 70 of the oil scraper ring 7 to the outer side of the piston 1 and onto the cylinder wall, while another part of the oil is directly flung back by the piston to the interior of the engine. Moreover, the piston is cooled by the oil jet or jets 10 impinging on the inner wall of the piston. On the other hand, the oil thus passed to the wall of the cylinder or to the working surface'of the piston at first causes a thorough lubrica tion of the latter as indicated by the arrows 17, but is then forced into the return channels 13, as indicated by the arrows 17a, owing to the pressure existing between the working surface of the piston and the cylinder surface, and allowed to flow oif freely in a downward direction through said channels 13, as indicated by the arrows 16. Owing to the said sufficient depth of the return channels, an intensive shaking-01f effect will occur especially in the inner or lower dead center, on reversal of the stroke, whereby the oil fed in large quantities is flung out of the channel or gap 13, towards the crank case, and a cor responding intensive circulation is ensured.

Where a lateral lower guide strip 18, Figs. 1 and 3, is indispensable, thesame will be interrupted by a plurality of groove-shaped channels 19 forming a continuation of the respective channel 13 and ensuring the downward flow of the oil and the circulation thereof as hereinbefore described. Fig. 2 shows the arrangement of the guide strip 18 with channels 19 interrupting the same. Of course, the depth of the channels 13 and 19 has been greatly exaggerated, for the sake of better illustration.

It will be understood, moreover, that an efficient lubrication of the working surfaces of the piston exposed to the normal pressure resulting from the gas pressure is very important in order to reduce the friction of the piston. A

To this end, according to the present invention the bearing strips on the piston skirt are shaped in such a way, as shown in Figs. and 7, that the working surface of the bearing strip 22 on the pressure side of the piston, i. e., the side engaging the cylinder wall during the expansion stroke of the piston, indicated by the arrow 27 in Fig. 5, is enlarging from 24 to 23, i. e. from the lower end of the piston skirt towards the piston head 21, as indicated in Fig. 4, while the working surface 22' of the piston on the side engaging the cylinder wall during the compression stroke of the piston, indicated by the arrow 27a in Fig. 7, is enlarging in a reverse direction, i. e. from the piston head 21 towards the lower end 24 of the piston, as shown in Fig. 7. Advantageously these carrier strips are enlarged according to a trapezoidal shape. In, most instances, each of said carrier strips will extend over an area of 2 x 45 in the direction of oscillation of the connecting rod 11 whose piston pin 31 is indicated in dotted lines, while the grooves or channels 13 for returning the lubricating oil are arranged therebetween, as shown, these channels or clearance cuts 13 extending up to the edges 26. Therefore, these edges 26 normally are poorly lubricated and tend to rubbing whereby the frictional losses are increased. The trapezoidal formation of the bearing strips 22, 22' provides an additional efficient lubrication of said edges as follows:

When the piston has passed its upper dead center position, at the beginning of its expansion stroke, the pressure side of the piston, exposed in Fig. 5, will engage the cylinder surface and the piston will start its downward motion. As a result of the pressure exerted between the bearing strip 22 of the piston and the cylinder wall, the oil, exemplified by a particle indicated at 29, will tend to flow towards the channel or clearance 13, from the working surface 22 of the piston, on the path indicated by the-dotted line 28. Owing to the adherence of the oil particle 29 on the cylinder wall and owing to the clearance at 13, the oil particle when having reached the clearance 13 will not be taken along by the piston but sticks to the cylinder wall. Hence, it will travel in relation to the piston in an opposite direction of the motion 27 of the piston, i. e. in an upward direction, thus coming against the inclined edge 26 of the bearing strip, at 30. The edges 26 of the bearing strip 22 are preferably rounded 01f, so as to enable the oil particle to re-enter between the bearing strip 22 and the cylinder surface. The same effect will occur in an opposite direction on the opposite side, shown in Fig. 7, in case of the upward or compression stroke of the piston, in the direction of arrow 27a.

It will be understood that the critical parts of the working surface of the piston, more particularly the edges of the bearing strips, are thus continuously supplied with fresh oil, whereby the total friction and wear of the piston is substantially reduced.

While the invention has been described in detail with respect to certain now preferred examples and embodiments of the invention it will be understood by those skilled in the art after understanding the invention that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended, therefore, to cover all such changes and modifications in the appended claims.

I claim:

1. In a piston engine having a crankcase, a cylinder in said crankcase, a piston in said cylinder, an exteriorly circumferentially grooved oil scraper ring on said piston, and oil passage means extending from the interior of the piston to the grooved portion of said ring, and further comprising means for injecting oil into the interior portion of said piston and through said oil passage means to .cool said piston and lubricate said cylinder, and channel means in said piston skirt extending from said ring to the free end of said skirt and circumferentially covering a substantial portion of the surface of said skirt for freely draining oil from said ring down to and off of said free edge.

2. In a piston engine as in claim 1, said channel means further comprising channels having a depth of at least 0.5 mm.

3. In a piston engine as in claim 2, said channels further covering substantially of the piston skirt surface.

4. In a piston engine as in claim 3, said channels further being located on the non-pressure sides of said piston.

5. In a piston engine as in claim 4, further comprising a grooved guide strip adjacent the free end of said skirt.

'6. In a piston engine as in claim 1, said channel means further comprising a pair of channels diametrically opposed on the non-pressure sides of said piston and increasing in width from the free end of said skirt toward said ring.

7. In a piston engine as in claim 1, said channel means further comprising a pair of channels diametrically opposed on the non-pressure sides of said piston and decreasing in width from the free end of said skirt toward said ring.

8. In a piston engine as in claim 1, said channel means further comprising a pair of channels diametrically opposed on the non-pressure sides of said piston, one of the bearing surfaces between said channels increasing and the other of said surfaces decreasing in width from the free end of said skirt toward said ring.

References Cited in the file of this patent UNITED STATES PATENTS 878,783 Downie Feb. 11, 1905 1,231,901 Jones July 3, 1917 1,368,447 Megson Feb. 15, 1921 1,468,621 Alford Sept. 25, 1923 1,492,917 Bruegger May 6, 1924 1,528,817 Dinnes Mar. 10, 1925 1,772,931 Dusevoir Aug. 12, 1930 1,951,959 Alexandrescu Mar. 20, 1934 2,083,636 Caldwell et a1 June 15, 1937 2,092,599 Brill Sept. 7, 1937 2,396,018 Mis Mar. 5, 1946 FOREIGN PATENTS 80,419 Sweden May 15, 1934 

